[es7] Implement async functions parsing

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index dc503e96ed5e69705492fa097f533da5d6025515..69e7da5cb7145100dd8170c8c9f82e883fdf1e02 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -4276,7 +4276,7 @@ class ScopeInfo : public FixedArray {
   class HasSimpleParametersField
       : public BitField<bool, AsmFunctionField::kNext, 1> {};
   class FunctionKindField
-      : public BitField<FunctionKind, HasSimpleParametersField::kNext, 8> {};
+      : public BitField<FunctionKind, HasSimpleParametersField::kNext, 9> {};
 
   // BitFields representing the encoded information for context locals in the
   // ContextLocalInfoEntries part.
@@ -6751,6 +6751,9 @@ class SharedFunctionInfo: public HeapObject {
   // Indicates that this function is a generator.
   DECL_BOOLEAN_ACCESSORS(is_generator)
 
+  // Indicates that this function is an async function.
+  DECL_BOOLEAN_ACCESSORS(is_async)
+
   // Indicates that this function is an arrow function.
   DECL_BOOLEAN_ACCESSORS(is_arrow)
 
@@ -7035,6 +7038,7 @@ class SharedFunctionInfo: public HeapObject {
     kDontCrankshaft,
     kDontFlush,
     kIsArrow,
+    kIsAsync,
     kIsGenerator,
     kIsConciseMethod,
     kIsAccessorFunction,
@@ -7050,7 +7054,7 @@ class SharedFunctionInfo: public HeapObject {
   // Add hints for other modes when they're added.
   STATIC_ASSERT(LANGUAGE_END == 3);
 
-  class FunctionKindBits : public BitField<FunctionKind, kIsArrow, 8> {};
+  class FunctionKindBits : public BitField<FunctionKind, kIsArrow, 9> {};
 
   class DeoptCountBits : public BitField<int, 0, 4> {};
   class OptReenableTriesBits : public BitField<int, 4, 18> {};